Bolsters are commonly used in the construction industry for the support of post-tension cables, rebars, or mesh above a surface. Typically, when such materials are used, they must be supported above the surface when the concrete is poured. These bolsters are used with poured decks. In normal use, the bolster is positioned on the deck and includes a beam which extends across a plurality of leg members. This beam is formed so as to contact and support the rebar while the base of the bolster rests on the deck or on a grade. When the concrete is poured, the bolster will support the rebar a proper distance above the bottom surface.
In normal use, such bolsters are preformed so that they can be installed quickly and easily upon the deck. Conventionally, the preformed bolster will have a plurality of leg members and a steel rod welded to a top surface of each of the leg members. The rod will serve as a receiving area for the rebar. Conventionally, these bolsters are formed in preset lengths. If it is necessary to extend the bolster across a long surface of the deck, then the ends of the beams of adjacent bolsters will be wired together such that the bolsters are in an end-to-end relationship.
The most common bolster that is employed is a metal bolster manufactured by Meadow Steel Products of Tampa, Fla. This bolster has a plurality of inverted U-shaped leg members having outwardly extending foot portions. A rigid tubular rod having a slight waveform pattern formed thereon is welded to the middle of the inverted U-shaped leg members. Each of the leg members is generally arranged in parallel relationship to each other. The feet of each of the leg members will rest on the deck while the rebar is supported. After the concrete has solidified, and the deck is removed, the bottom surfaces of the feet will be exposed. As such, it is necessary to coat the feet with an anti-rust material. Alternatively, stainless steel material can be employed for the leg members and their associated feet.
Corrosion and cost are major problems affecting the bolster of Meadow Steel Products. In order to form such a bolster, a great deal of manufacturing must take place, including metal forming, bending, dipping, and welding. These activities, along with the cost of the material used to form the bolster, make the cost of the bolster relatively expensive. If the bolster is not coated or made of a stainless steel material, then corrosion can adversely affect the product. This corrosion can even occur when the metal is coated.
In the past, various attempts have been made to create bolsters of plastic material that can serve the purposes of the bolster of Meadow Steel Products. In general, such efforts have resulted in plastic chairs that are ineffective, cumbersome to use, or unable to properly withstand the forces imparted by the rebar upon the bolster. One such plastic bolster, manufactured by Conac, includes a central beam which is integrally formed with a plurality of leg members. Each of the leg members extends downwardly so as to present a flat surface to the underlying deck. No feet are provided which allow the bolster to be stapled to the deck. Additionally, the configuration of this Conac bolster allows for easy deformation. It is very difficult and time consuming to join lengths of the Conac bolster together. The Conac bolster also lacks the suitable wave form pattern for the receipt of the rebar on the top surface of the bolster. This plastic bolster is often broken, collapsed, or tipped over in actual use. The base of such a bolster has only a very small area of contact with the deck. As such, these plastic bolsters lack the strength and ability to withstand the loads imparted to them.
U.S. Pat. No. 5,664,390, issued on Sep. 9, 1997 to the present inventor, describes a bolster for use in construction. This bolster has a plurality of leg members arranged in parallel relationship and a beam integrally formed with the plurality of leg members and extending across the plurality of leg members. Each of the plurality of leg members has a foot for contacting the underlying surface. Each of the leg members includes a central body portion, a first leg extending downwardly from one side of the central body portion and a second leg extending downwardly from an opposite side of the central body portion. The foot is formed at an end of each of the first and second legs opposite the central body portion. The foot includes a plurality of pin-like projections extending outwardly from a bottom surface thereof. This bolster is of a type for stapling and fixed attachment to an underlying deck. However, under certain circumstances, it would be desirable to be able to use these bolsters for “upper beam” purposes. Upper beam bolsters are often used upon the top of mesh or layers of strands. The upper beam bolsters are commonly used in highway construction where multiple layers of steel are laid out. Under other circumstances, a widened or flat base is required for slab-on-grade construction. The relatively small and narrow feet would sink into sand or dirt if the bolsters of U.S. Pat. No. 5,664,390 were used for “upper beam” purposes. In other circumstances, upper beam slab bolsters are used on corrugating steel decking so as to be in flat surface-to-surface contact with such steel flat surfaces. As such, a need has developed so as to allow the bolster of U.S. Pat. No. 5,664,390 to be properly adapted for upper beam bolster purposes.
The present inventor has filed U.S. application Ser. Nos. 10/223,042 and 10/223,044 on Aug. 19, 2002 for plates for use with such upper beam slab bolsters. In each of these cases, the upper beam bolster that is used in of a type that is formed by injection molding. Whenever injection molding processes are used, the cost of preparing a die is relatively expensive. Ultimately, the cost of the die can determine the profitability or lack of profitability of a particular plate construction. In view of the limited application for such injection-molded plates for upper beam slab bolsters, it was found that the injection molding of such plates reduce the economic advantage associated with attaching a plate to an existing bolster. As such, a need developed in which to reduce the costs associated with the manufacture of such plates for upper beam slab bolsters.
It is an object of the present invention to provide an upper beam slab bolster that is corrosion-proof and relatively inexpensive.
It is another object of the present invention to provide an upper beam bolster which can be made from an easily assembled bolster and support plate.
It is another object of the present invention to provide an upper beam bolster that can withstand the forces imparted to it.
It is a further object of the present invention to provide an upper beam slab bolster that includes a bottom plate that can be formed through extrusion molding processes.
It is still a further object of the present invention to provide an upper beam bolster that is easy to manufacture and easy to use.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.